This invention relates to a novel method for intaglio printing and to a novel inking plate therefor. In the novel method, which is particularly useful for printing changeable markings, such as bar-coded markings representing serial numbers, on nonabsorbent surfaces, the depressed or intaglio areas of the inking plate can be changed on demand.
There are several printing machines on the market today that are able to print serial markings, such as serial bar-code markings, on paper or other soft absorbent materials. The techniques employed by these printers usually require building the marking out of a series of dots or bars in a sequential fashion. These machines are currently not capable of printing on hard, nonporous, irregular surfaces because of the unyielding nature of the printing elements and/or the slow drying nature of the ink.
In a prior offset pad printer, such as the unit described in U.S. Pat. No. 4,060,031 to W. Philipp, a very compliant printing pad transfers an ink pattern from etched shallow depressions in an intaglio inking plate to the receiving surface to be printed. Typically, the depressions in the inking plate are made by a photoengraving technique so that areas on the inking plate that have been etched correspond to the inked parts of the printed marking. In the full cycle, ink is dragged out of an adjacent reservoir and distributed over the inking plate surface to fill the depressions. Then, a doctor blade removes the excess ink and returns it to the reservoir so that the area around the depressions to be transferred is clean and ink fills the depressions. The pad then contacts the inking plate, thus picking up the pattern of ink from the depressions and carries the pattern to the receiving surface already prepared to accept the ink. In the next cycle, ink is again distributed over the plate surface to refill the depressions in the inking plate so that the process can be repeated.
The prior offset pad printer is effective to print fixed, and sometimes complicated, patterns on hard, nonplanar, irregular surfaces of nonabsorbent materials. The novel method disclosed herein can convert the prior intaglio printing method and inking plate to be capable of printing different markings, instead of the same fixed markings, on any surface, but particularly on hard, irregular surfaces of nonabsorbent materials.